This application claims prior of Japanese Patent Application No. 11-31936, filed Feb. 9, 1999, the entire disclosure of which is hereby incorporated by reference.
(a) Field of the Invention
The invention relates to positive photosensitive resin compositions, particularly to positive photosensitive resin compositions which, on heating, become heat-resistant polyimide polymers suitable for surface-protecting films, interlayer insulating films and others for electronic parts such as semiconductor elements. It also relates to methods of forming relief patterns and to electronic parts using such compositions.
(b) Description of the Related Art
Polyimides have good heat rsistance and good mechanical properties, and are readily formed into films of which the surface could be well planarized. Having those advantages, they are widely used for surface-protecting films, interlayer insulating films and others for semiconductor devices. Where polyimides are used for surface-protecting films or interlayer insulating films, forming through-holes and the like in such films is achieved mainly by etching processes using positive photo-resists. Such processes, however, involve steps of appying and removing the photo-resists, which complicate the processes. To simplify the working process, heat-resistant materials with photosensitivity have heretofore been studied.
As to photosensitive polyimide compositions, for example, known are (a) a polyimide precursor composition in which is introduced photosensitive groups through ester bonding (Japanese Patent Application Examined Publication No. 52-30207), and (b) a polyamidate composition in which is added a compound that has carbon-carbon double bonds capable of being dimerized or polymerized by the action of chemical rays, amino groups and an aromatic bisazide (Japanese Patent Application Examined Publication No. 3-36861). To form patterns, photosensitive polyimide precursor compositions are generally applied in solution form onto a substrate and dried, and then exposed to active rays via a mask and developed.
The compositions (a) and (b), however, require an organic solvent as a developer. When waste developers are treated, the large quantities of developers that are several times that of the photosensitive polyimide precursor compositions load the environment heavily. In recent years, for the preservation of the environment, there has been increasing demand for photosensitive polyimide compositions that are developable with aqueous developers and enable easy treatment of waste developers. Further, the compositions (a) and (b) are both negative ones, and involve the problem that the mask for exposure needs to be changed to switch from an etching process using positive photo-resists to the process using negative photosensitive polyimide precursors.
As to positive photosensitive polyimide precursor compositions, for example, known are (c) a polyimide precursor in which is introduced an o-nitrobenzyl group through ester bonding (Japanese Patent Application Unexamined Publication No. 60-37550), (d) a composition comprising a polyamidate and an o-quinonediazide compound (Japanese Patent Application Unexamined Publication No. 2-181149), (e) a composition comprising a carboxyl group-having polyamidate and an o-quinonediazide compound (Japanese Patent Application Unexamined Publication No. 4-168441), and (f) a composition comprising a hydroxyl group-having polyamidic acid or polyamidate and an o-quinonediazide compound (Japanese Patent Application Unexamined Publication No. 3-115461).
Incidentally, semiconductor elements have been increasingly integrated with years, requiring improved fine processing techniques. A means for enabling fine processing is exposure using light of shorter wavelength, and g-line (wavelength: 436 mn), which have been mainly used as the exposure light to pattern positive photo-resists, are being replaced by exposure to i-line (wavelength: 365 nm). Accordingly, photosensitive polyimide precursors are also required to be able to form patterns with i-line, to accommodate them to exposure apparatuses using i-line.
The positive photosensitive polyimide precursor composition (c), however, is sensitive mainly to lights of wavelengths of 300 nm or less, and has poor sensitivity to i-line. The positive photosensitive resin compositions (d) and (e) have the shortcoming of poor storage stability. The Japanese Patent Unexamined Publication No. 3-115461 does not disclose or suggest exposure with i-line, and the positive photosensitive resin composition (f) disclosed therein, in fact, has poor sensitivity to i-line.
An object of the invention is to solve the problems in the above-described prior art by providing a positive photosensitive resin composition which is highly sensitive to lights including i-line and has good storage stability.
Accordingly, the invention provides a positive photosensitive resin composition comprising:
(A) a polyamidate having repetitive units of general formula (I) 
wherein R1 is a tetravalent organic group, R2 is a divalent organic group having a phenolic hydroxyl group, three R3 groups and three R4 groups each independently are an alkyl group or a hydrogen atom, and at least two R3 groups and at least two R4 groups are alkyl groups, and
(B) a compound capable of generating an acid when exposed to light.
Another object of the present invention is to provide a positive photosensitive resin composition to be used for exposure with i-line.
Accordingly, in one embodiment, the positive photosensitive resin composition is to be exposed to i-line.
Another object of the present invention is to provide a positive photosensitive resin composition which further has good heat resistance.
Accordingly, in one embodiment, the group represented by R1 is a tetravalent organic group which has a condensed polycyclic structure consisting of 2 to 5 benzene rings or a polycyclic structure wherein two or three aromatic rings are linked to each other through one or two bonds selected from the group consisting of a single bond, an ether bond (xe2x80x94Oxe2x80x94), an isopropylidene bond (xe2x80x94C(CH3)2xe2x80x94), a hexafluoroisopropylidene bond (xe2x80x94C(CF3)2xe2x80x94), a sulfone bond (xe2x80x94SO2xe2x80x94), a methylene bond (xe2x80x94CH2xe2x80x94) and a carbonyl bond (xe2x80x94COxe2x80x94), and the group represented by R2 is a divalent organic group which has an aromatic ring or a polycyclic structure wherein two or three aromatic rings are linked to each other through one or two bonds selected from the group consisting of a single bond, an ether bond, an isopropylidene bond (xe2x80x94C(CH3)2xe2x80x94), a hexafluoroisopropylidene bond, a sulfone bond, a methylene bond and a carbonyl bond, and has at least one phenolic hydroxyl group.
In one embodiment, the tetravalent organic group represented by R1 is selected from the group consisting of 
and the group xe2x80x94C(xe2x95x90O)OC(R3)3 is linked to R1 at an ortho or peri position relative to one of the amide bonds, and the group xe2x80x94C(xe2x95x90O)OC(R4)3 is linked to R1 at an ortho or peri position relative to the other amide bond;
and the divalent organic group represented by R2 is selected from the group consisting of 
Another object of the invention is to provide a positive photosensitive resin composition which has good storage stability and is particularly highly sensitive to lights including i-line.
Accordingly, in one embodiment, the invention provides a positive photosensitive resin composition which comprises
(Axe2x80x2) a polyamidate having repetitive units of general formula (Ixe2x80x2) 
wherein R1 is a tetravalent organic group, R6 is a divalent organic group selected from 
three R3 groups and three R4 groups each independently are an alkyl group or a hydrogen atom, and at least two R3 groups and at least two R4 groups are alkyl groups, and
(B) a compound capable of generating an acid when exposed to light.
Another object of the invention is to provide a positive photosensitive resin composition which is less shrinkable when heat-treated after development.
Accordingly, in one embodiment, the groups represented by xe2x80x94C(R3)3 and xe2x80x94C(R4)3 are isopropyl groups, sec-butyl groups or 1-methylbutyl groups.
Another object of the invention is to provide a positive photosensitive resin composition which is particularly sensitive to lights including i-line.
Accordingly, in one embodiment of the invention, the tetravalent organic group represented by R1 is selected from the group consisting of 
In one embodiment, the component (B) is selected from the group consisting of an o-quinonediazide compound, an aryldiazonium salt, a diaryliodonium salt and a triarylsulfonium salt.
Another object of the invention is to provide a positive photosensitive resin composition which is also excellent particularly in sensitivity.
Accordingly, in one embodiment, the component (B) is an o-quinonediazide compound.
In one embodiment, the o-quinonediazide compound is obtainable by condensation of an o-quinonediazidosulfonyl chloride with a hydroxy compound or an amino compound in the presence of a dehydrochlorinating catalyst.
In one embodiment, the positive photosensitive resin composition of the invention contains 3 to 100 parts by weight of the component (B) relative to 100 parts by weight of the component (A).
In a preferred embodiment, the positive resin composition of the invention contains 5 to 40 parts by weight of the component (B) relative to 100 parts by weight of the component (A).
Another object of the invention is to provide a method of forming relief patterns with good profile by using a positive photosensitive resin composition which is highly sensitive to i-line and has good storage stability.
Accordingly, the invention provides a method of forming a relief pattern, comprising a step of applying the positive photosensitive resin composition of the invention onto a substrate and drying it thereon to form a coating film, a step of exposing the coating film to i-line, a step of developing the exposed coating film, and a step of heating the developed coating.
Another object of the invention is to provide a highly reliable electronic part by incorporating therein polyimide patterns having high heat resistance and good mechanical properties.
Accordingly, the invention provides an electronic part containing the relief pattern formed by the method of the invention as a surface-protecting film or an interlayer insulating film.